Ecological Pest Management

Growers can often manage pests by expanding the diversity of plants and animals in farm fields. This issue of ATTRAnews describes ways to protect crops through biodiversity and
other practical strategies.

Why On-Farm Biodiversity Makes $ense

Rex Dufour, NCAT Agriculture Specialist

Pest management is an ecological matter. The size of a pest population and the damage
it inflicts will depend on the design and management of an agricultural ecosystem. If
the system design is faulty—making it easy for pests to develop or making it difficult
for their natural enemies—then farmers will have to expend unnecessary resources
(think: energy costs) for pest management.

We've come to accept routine use of biological poisons and fertilizers made from
fossil fuel. But continuous application of these chemicals represents significant energy
inputs into the agricultural system, and carries both obvious and hidden costs to the
farmer and society. Substituting chemical inputs for ecological design is an increasingly
expensive, never-ending cycle, and an exercise in futility and inefficiency.

Photos courtesy of R.B. Dufour and K.R. Dufour

Ecological pest
management uses common-sense principles to deal with pests and their parasites and predators.
The idea is to increase the environmental pressure against pests, and provide habitat for beneficial organisms. You want to creatively manipulate your cropping systems to your advantage.

Many seemingly small interactions
in an agricultural ecosystem can combine to create effective pest management and overall health of the farm system. Don't be shy—Biodiversify!

Save Money and
Energy with Ecological Pest Management

Ecological pest management is based on preventing pest problems before
they happen. With this approach, farmers can avoid the costs of pesticides as well as the fuel,
equipment and labor used to apply them.

In the
July 2005 issue of BioScience, Cornell University researcher Dave Pimentel reviewed a 22-year trial
comparing conventional and organic corn/soybean systems: "Organic farming approaches for these crops
not only use an average of 30 percent less fossil energy," he reported, "but also conserve more water
in the soil, induce less erosion, maintain soil quality, and conserve more biological resources than conventional farming does."

Unsung Heroes - Bats and Spiders

Bats and spiders are generally not "top of the list" animals when producers think about creating a healthy farm.
But every farm should provide habitat for them because of the pest control benefits they provide.

Bats: Most bats are insect-eaters. Found in every state of the U.S., bats prey at night on adult forms of critters that farmers don't like—armyworms, cutworms, codling moths, cucumber beetles, stinkbugs, June bugs, and mosquitoes.

Bats can be invited onto a farm by putting
up a bat box, or by making simple
modifications to a farm building. For more information
about bat habitat and which bats live in
your region, contact your state Fish and
Game Department or Bat Conservation International,
www.batcon.org/home/default.asp

Spiders: Like bats, spiders are generalist
predators, devouring many kinds of
insects. For centuries the Chinese have
augmented spider populations in field
crops as a pest management strategy.
Spiders are able to rapidly colonize an
area by parachuting on a silk thread—a
practice known as ballooning. Spiders
are often the earliest predaceous colonizers
of agricultural fields.

Unlike insects, spiders have a soft
external skeleton, making them more
vulnerable to extremes of temperature or
humidity, so mulching or no-till cropping
techniques help promote spider populations.
A study in Germany found that
mulch increased spider densities in wheat
fields, and thereby reduced cereal aphid
populations by 25%. Researchers have also noticed an interesting fact about spiders:
their presence causes some insect pests to
abandon their host plant, decreasing damage
to crops. This has been observed for cucumber
beetles, Japanese beetles, cutworms,
greenbugs, leafhoppers, planthoppers, and
for moth larvae in apple orchards.

Spiders often kill more insects than they
can consume, but each species of spider
has its own food and habitat preferences.
To attract a wide range of spiders that will
prey on many different kinds of pests,
farmers can plant hedgerows in or adjacent
to fields. It's a good idea to include perennial
and annual plants of different heights,
as well as groundcovers and mulches. For
more information: rexd@ncat.org

ATTRA's Organic Integrated Pest Management (IPM) Field Guide

This pictorial series highlights:

Beneficials, Beneficial Habitat, and Insect Pests

Plant Disease Management

Weed Management

Vertebrate Pest Management

Filled with color photos that show the details you need, these guides feature beneficial organisms as well as harmful pests. The focus is on how to prevent insect and vertebrate pests, diseases, and weeds from becoming a problem in the first place. Brief text provides useful take-home messages for farmers about what the critter eats and how to manage it. Available in English (IP257) and Spanish (SP257), both online and in CD format.

Perimeter Trap Cropping to Attract and Remove Insect Pests

Farmers can grow an insect pest's favorite host plant
around the edge of fields to attract and "hold" the pest away
from the main crop. The trick is to completely surround the
field and then to manage the pests in the trap crop.

For Cucumber Beetles in Squash & Cucumbers: Plant one
or more rows of Hubbard squash (the trap crop) around
the perimeter of fields of summer squash, butternut, and
cucumbers. Begin scouting the outer trap crop rows for cucumber
beetles as soon as the plants emerge or within days
of completing transplant operations.

Spray to kill cucumber beetles when they begin feeding
on the trap crop. Scout for beetles twice weekly. Prevent
the beetle population from killing and overrunning the
perimeter plants. For the barrier to function, it is crucial
to maintain the health and attractiveness of the trap crop
plants. To learn more: T. Jude Boucher, University of
Connecticut Co-op Extension, 860-875-3331,
www.hort.uconn.edu/ipm

For Pepper Maggot Fly in Bell Peppers: Using hot cherry
peppers as a perimeter trap crop, growers have reduced
insecticide use by up to 89%. They report the system simplifies pest control and saves money. Economic analysis
confirms an improvement in crop profitability of between
$13 and $378/hectare. To learn more:
T. Jude Boucher (see above): www.hort.uconn.edu/IPM/veg/htms/trpcrops.htm

ATTRA Publications about Ecological Pest Management

These publications—and many more on specific techniques, crops, pests, and diseases—can be downloaded for free from the
ATTRA website's pest management section, http://attra.org/pest.html. Or call 800-346-9140 for a printed copy.

Healthy Soil: The Foundation of Ecological Pest Management

"We are what we eat." This folk wisdom
relates to plant health as well as to human
health. Any organism that consumes
a poor diet will be stressed and
susceptible to a variety of ills.

The soil is the primary source of nutrition
for plants. If the soil is unhealthy,
with low levels of organic matter, poor
biological activity, and unbalanced nutrients,
plants are likely to be more susceptible
to attacks by various pests and
diseases, and less able to recover from
these attacks. The grower, in turn, will
have to spend resources—management
time, money, machinery, chemicals—to
address pest infestations that may only
be symptoms of poor soil health.

Fair Trades in the Root Zone
Plants and soil organisms evolved together
for hundreds of millions of years
in non-agricultural systems. They developed
symbiotic partnerships that give
plants the water and nutrients they need
to successfully grow and reproduce.
The area immediately surrounding the
plant root—known as the rhizosphere—is densely populated with bacteria and
fungi. This is not surprising, since roots
exude carbon compounds (sugars, etc.)
that are used by fungi and bacteria.
These root secretions bring minerals
to the roots through a range of very
complex interactions that depend on the
plant, soil type, and soil health.

In undisturbed soils, mycorrhizal
fungi respond to the root secretions by
forming a layer dense enough to protect
the root surface from disease organisms.
Mycorrhizal fungi also enter the
root itself and provide the plant with
water and various soil nutrients in
exchange for the carbon compounds
that roots secrete. The mycorrhizae are
able to "mine" a volume of soil much
greater than the plant roots could reach.
It seems a fair trade.

Mycorrhizae have another positive
effect on plants. They can cause
the plant to produce compounds that
protect it against pathogens and insects.
Some of these protective compounds
are antioxidants, which have recently
been shown to provide health benefits
to humans. They have been found in
higher concentrations in some organically
grown produce than in conventionally
grown produce.

What happens in unhealthy soils?
In poorly managed soil, the plant roots
exude greater carbon in an apparent
effort to mobilize the minerals that are
deficient in the soil. This extra effort
weakens the plant, making it more
attractive to insect pests and reducing
crop production.

In frequently tilled soils, many of the
beneficial organisms disappear because
organic matter is destroyed and pesticides
and fertilizers are applied. Without
the beneficial organisms, there is a much
greater likelihood that harmful species of
bacteria, fungi, and nematodes will grow
and develop on the plant roots.

So the bottom line is that healthy
soils translate into healthy, pest-resistant
plants and ultimately into healthy,
disease-resistant animals and people.

When Soil is Tilled

Dr. Elaine Ingham, soil microbiologist
and founder of Soil Foodweb, Inc., describes
an undisturbed grassland—where
a wide diversity of plants grow, their
roots mingling with a wide diversity of
soil organisms—and how it changes when
it becomes a field of row crops.

A typical teaspoon of native grassland
soil contains between 600 million
and 800 million individual bacteria
that are members of perhaps 10,000
species. Several miles of fungi are in
that teaspoon of soil, as well as 10,000
individual protozoa. There are 20 to
30 beneficial nematodes from as many
as 100 species. Root-feeding nematodes
are quite scarce in truly healthy
soils. They are present, but in numbers
so low that it is rare to find them.

After only one plowing, a few
species of bacteria and fungi disappear
because the food they need is
no longer put back in the system.
But for the most part, all the suppressive
organisms, all the nutrient
cyclers, all the decomposers, all the
soil organisms that rebuild good soil
structure are still present and trying
to do their jobs.

Why doesn't the reduced food
supply have a greater effect? A good
savings account of organic matter has
been built up in native grassland and
native forest soil. The soil organisms
use the organic matter they "put
away" all those years when disturbance
did not occur.

But agricultural tillage continues
to deplete soil organic matter and
kill fungi. The larger predators are
crushed, their homes destroyed. The
bacteria go through a bloom and blow
off huge amounts of that savings-account
organic matter. With continued
tillage, the "policemen" (organisms)
that compete with and inhibit disease
are lost. The "architects" that build
soil aggregates are lost. So are the "engineers"—the larger organisms that
design and form the larger pores in
soil. The predators that keep bacteria,
fungi, and root-feeding organisms in
check are lost. Disease suppression
declines, soil structure erodes, and
water infiltration decreases because
mineral crusts form. (From "Replacing
Methyl Bromide with Compost."
BioCycle, December 1998)

Solarization: Using the Sun's Energy to Fight Pests

By Martin Guerena, NCAT Agriculture Specialist

Imagine harnessing the sun's energy to destroy your enemies. Like Archimedes—the
ancient Greek whose "solar death ray" used mirrors to burn a Roman fleet—farmers
can destroy or disable insects, diseases, nematodes, and weeds in the field. The
technique known as solarization consists of laying a clear plastic tarp on moist soil and letting the sun's rays heat the soil.

Heat is trapped under the plastic, raising the soil temperature to kill or debilitate
pests. Most of the research worldwide has concentrated on hot and arid areas, but
anyplace with hot summers has the potential to use this system.

Usually this soil pasteurization process takes 4-6 weeks, but the amount of time
depends on many factors, such as rain, wind, day length, soil texture, and the quality
of the polyethylene tarp. Ultraviolet-protected plastic is recommended so the tarp
can be removed and re-used.

Certain types of organic matter can be added to the soil for "bio-fumigation." Residues
from brassica crops such as broccoli and mustards, for example, have shown
this bio-fumigant effect. When heated in the solarization process, they release volatile
compounds that are toxic to many pests.

Before solarization takes place, the land where the crop is to be seeded or transplanted
must be prepared for planting. Beds must be shaped, drip tape installed,
and fields leveled. This is to avoid stirring up the soil after solarization, which
would bring fresh pest organisms to the soil surface.

Special Caution: Drip tape must be buried at least an inch deep to avoid damage
from the sun's rays. In experiments where the tape was placed on the surface of the
bed and then covered with the clear plastic, the drip tape was damaged by the magnifying
effect of the sun on the water droplets that condensed on the plastic.

Depending on the outside temperature, sunlight density, and the type of pests, soil
solarization can provide good pest control 8 to 10 inches deep, although best control
is generally obtained down to 6 inches.

New and Updated Publications from ATTRA

ATTRAnews is the bi-monthly newsletter of ATTRA - National Sustainable Agriculture Information Service. The newsletter is distributed free throughout the United States to farmers, ranchers, Cooperative Extension agents, educators, and others interested in sustainable agriculture. ATTRA is funded through the USDA Rural Business-Cooperative Service and is a project of the National Center for Appropriate Technology (NCAT), a private, non-profit organization that since 1976 has helped people by championing small-scale, local and sustainable solutions to reduce poverty, promote healthy communities, and protect natural resources.